The problems arising with the use of electrosurgical instruments where the field of view of the surgeon is limited are well-known. Traditional laparoscopic electrosurgical tools include a trocar sheath or other cannula that is inserted into a patient's body and that provides a conduit for a surgeon to introduce various surgical cutting tools, optics for increased visualization, irrigation, active surgical electrodes, and other devices to be used during a surgical procedure.
One problem arises if the insulation on the active electrode is damaged thereby allowing the active current (possibly in the form of arcing) to pass there-through directly to the patient's tissue whereby unintended and potentially unknown injury, possibly in the form of a life threatening infection, can occur. The arcing may occur out of the surgeon's field of view which may extend as little as about 2 centimeters from the tip of the active electrode (or the surgical field). The field of view is typically established by illumination and viewing sources. In the context of prior art laparoscopic instruments, the illumination and/or viewing sources are established through one or more other trocar sheaths at other incisions.
Particularly with electrosurgical instruments, there can be many centimeters of the active electrode which extend between the entry point in a patient's body and the surgeon's field of view, typically at the distal end of the active electrode and near the point where electrosurgery takes place. The area of the electrosurgical instrument, and in particular the active electrode, that is out of the field of view of the surgeon is potentially dangerous if left in an unmonitored state. In this situation, the insulated active electrode may unintentionally come into contact with unknown tissue of the patient may cause serious injury that might not be noticed by the surgeon during the procedure.
If arcing resulting from the damaged insulation were to occur within the field of view of the surgeon, the surgeon would normally observe this and immediately deactivate the generator. Arcing, however, is prone to occur at a site remote from the field of view of the surgeon, and as a consequence, damage to the active electrode insulation is particularly a problem because it may go undetected while the full active current passes through an unintended path of the patient's tissue from the active electrode to the return electrode.
A second problem that can arise is caused by a capacitive effect where one electrode of the capacitance is the active electrode and the other electrode of the capacitance is the metallic trocar sheath. The dielectric between these elements is the insulation on the active electrode. Current from the active electrode will be capacitively coupled to the trocar sheath and then returned through the body and the return electrode to the generator. If this current becomes concentrated, for example, between the trocar sheath and an organ such as the bowel, the capacitive current can cause a burn to the organ.
With respect to the use of laparoscopic electrosurgical tools, the above problems have been preliminary addressed by the use of a safety shield and/or monitoring circuitry which serves to deactivate the electrosurgical generator and accompanying current flow if an abnormal condition occurs. For example, U.S. Pat. Nos. 5,312,401, 5,688,269, 5,769,841 and 6,494,877, assigned to Encision, Inc., describe solutions to these problems. All of the details of these patents are hereby incorporated into the present application by reference in their entirety.
U.S. Pat. No. 4,184,492, by Meinke, discloses, in general, a system in which a resecting apparatus includes a connection between an outer tube (metallic) and a lead means (the return electrode) with an impedance of 100-1000 ohms. The purpose is to minimize or avoid burns to the patient and user touching the metallic parts of the instrument. There may be a monitor included in the connections to display unsafe conditions and also reduce power.
The assignee of the Meinke patent, Karl Storz Endoscopy-America, Inc., has not, to this day, offered a monitored or otherwise protected resectoscope that embodies the description contained in the Meinke patent indicating that there were, and continue to be, significant hurdles in the implementation of such a monitored or protected system in a resectoscopic device. The complex design issues of modern resectoscopes and associated surgical techniques have not changed significantly since the Meinke patent and the same problems described therein persist today.
It is thus desirable to overcome the inherent problems associated with incorporating the use of shielded and/or monitored systems such as those disclosed in the prior art into devices such as resectoscopes and hysteroscopes and to give the same, or better, level of protection to patients that is achieved with those prior systems.
Conventional resectoscopes, such as those manufactured by Karl Storz, combine many features into a single device. Such devices are typical of the devices that are predominantly used in many urological and gynecological electrosurgical procedures. It is estimated that approximately 200,000 of the resectoscopic surgeries in the United States alone are performed with a Storz instrument. This represents approximately ⅔ of the total procedures performed each year. U.S. Pat. No. 6,755,826, assigned to Olympus, gives one example of some of the mechanical complexities of a resectoscope. The details of the '826 patent are hereby incorporated by reference into this disclosure in their entirety.
Resectoscopes, such as those manufactured by Karl Storz, involve complex mechanics and generally bulky construction when compared with laparoscopic devices. For example, resectoscopes employ many components, each of which must be used in combination in a single device. In laparoscopic procedures, several separate devices are typically used to perform the many functions of a resectoscope. These include optics, illumination, irrigation (both in and out), electrical function (RF power), and the mechanical linkages for operation of the cutting tools. In addition, user proximity to resectoscopic devices presents its own challenges and increased need to prevent current from energizing the components that are near the surgeons face. Since the surgeon's face is, in many situations can be close to metallic conductive optics, there is the potential for current to flow directly to the surgeon and cause injury.
There are several additional problems that need to be overcome in resectoscopic and like devices that are not addressed in the prior art and that have not been addressed in any currently available technology. For example, the 100 ohm impedance addressed in the Meinke '492 patent is not low enough to completely and/or adequately couple the harmful current away from the patient and the user. While it does cut down the current flow, it is not adequate for shunting fault currents through the return electrode, particularly in applications where instruments have metallic components (e.g., resectoscopic applications). The 100 ohm impedance disclosed in the Meinke '492 patent is meant to prevent alternate return current from flowing through the metal components to the generator return. 100 ohms is not high enough to do that completely and some portion of the total current could still be conducted and may be enough to cause a burn at the contact with wet tissue.
Finally, resectoscopes are subject to otherwise “normal” working element current surges due to blood and/or other conductive fluid tissue bridging the working element and active electrode. These current surges are normally present on only a temporary basis and may or may not represent a dangerous condition to the patient that requires intervention.
Although present devices are functional, they are not sufficiently accurate or otherwise satisfactory. Accordingly, an improved system and method are needed to address one or more of the various shortfalls of present technology and to provide other new and innovative features.